1. Field of the Invention
The present invention relates to circuit arrangements for signalling the read points in time to a recording unit for designational reading of information contained in binary elements.
2. Description of the Prior Art
Integrated circuits are being developed and utilized to an increasing degree for system components such as, for example, subscriber and exchange equipment of ISDN telecommunications networks. These circuits, predominantly realized in mask etching technique, each contain complete function complexes of the system components. Such a function complex, for example, can be a transmission-oriented method with which the information are transmitted via the lines in the subscriber line region of an exchange equipment. Circuits, as well as a circuit design developed for ISDN system components, are shown and disclosed in the publication "Telecom Report" Vol. 9, No. 4, 1986, pp. 230-234. The circuit design is based on an "IOM Architecture", i.e. on an ISDN-oriented interface concept. This interface concept essentially contains a serial, internal data interface and an ISDN-oriented interface that is referred to below as an IOM interface. The IOM interface is formed with a respective receiving and data line by way of which the information are serially transmitted predominantly with a data rate of 256 Kbit/s as well as a respective bit group (frame) clock line having 8 KHz clock frequencies signals and a bit clock line having 512 KHz bit clock frequency signals. The bit group clock defines the limits of the bit groups each comprising 32 bits within the serial information stream. Furtermore, each bit group is sub-divided into 4 sub-groups of 8 bits each, whereby the first two bit sub-groups are each allocated to an information (B)-channel of an ISDN base terminal and the third sub-group contains a monitoring channel and the fourth bit sub-group contains the ISDN signaling (D)-channel, 2 bits, as well as an activation and access channel. The transmission of the communications information via the individual data links is monitored in the monitoring channel. The activation channel is provided for the activation or, respectively, deactivation of a circuit following the IOM interface by a preceding circuit. Access onto the monitoring channel is controlled via the access channel.
Since the IOM interface represents a central interface in the circuit concept and represents one of the few access points onto the information flow in the subscriber line region of an ISDN exchange equipment that is arranged outside of these circuits, there is a desire to co-read and record the information communicated via the IOM interface designationally, for example, only the signaling channel, or into, particularly in the case of fault or, respectively, malfunction. Recording equipment or, respectively, protocol testers and "logic analyzers" equipped with memory devices are already known for recording the information and these continuously read and store serially-existing information, information represented with TTL voltage levels as well.